A police officer says the suicide bomber drove an explosives-laden car into the gate of the intelligence headquarters in Karrada district today afternoon, killing six civilians and five security personnel.
He added that 24 other people were wounded.
A medical official confirmed causality figures. Both officials spoke on condition of anonymity as they were not authorised to brief the media.
Since early this year, Iraq has been facing a growing Sunni insurgency with the Islamic State group and allied Sunni militants who have taken over areas in the country's west and north.